A network fault determination apparatus that determines a fault in a network formed by connecting a plurality of information communication devices is disclosed in the related art (see Japanese Laid-open Patent Publication No. 2005-252765, for example). The apparatus of Patent Document 1 specifies the cause of a failure in the network utilizing only warnings generated by the information communication devices without using information provided by a user. Specifically, the apparatus collects warnings through communication with the information communication devices, compares the collected warnings with warning generation patterns in a warning generation pattern table, and determines the cause of a warning corresponding to a warning generation pattern coinciding with the collected warnings as the main cause of the failure. The apparatus also identifies incommunicable information communication devices on the basis of the connection relationship of the information communication device which involved the main cause of the failure, and identifies incommunicable logical circuits on the basis of the state of the information communication devices on a logical line route.
However, the apparatus according to the related art discussed above does not consider the hierarchical relationship peculiar to the network. Therefore, it cannot be known whether a notification of an error in a device A is made due to a fault of the device A itself or made under influence of a device B in a level higher than the device A even though no fault is occurring in the device A. Thus, the apparatus may not be able to specify the device that is truly at fault.